Electrical disconnectors



Oct. 25, 1960 F. G. MacRAE 2,957,967

ELECTRICAL DISCONNECTORS Filed July l5, 1957 2 Sheets-Sheet 1 l l INVENTOR.

Ff 6. M46 m5 Oct. 25, 1960 G, MacRAE 2,957,967

ELECTRICAL DISCONNECTORS Filed July l5, 1957 2 SheetsSheet 2 INVENTOR. FRED 6. MAC PAE Unitedd States Patent Gtice ELECTRICAL DISCONNECTORS Fred G. MacRae, La Grange, Ill., assiguor to H. K. Porter Company (Delaware), Pittsburgh, Pa., a corporation of Delaware Filed July 15, 1957, Ser. No. 671,902

3 Claims. (Cl. 200-115) My invention is an electrical disconnector or circuit interrupter designed primarily for detecting, indicating, and neutralizing the effect of, a failed lightning arrester, whether or not the failure of the lightning arrester is caused, or immediately preceded, by the discharge to ground of lightning or a surge of steep wave front, and which permits the discharge to ground of lightning or surges of steep wave front without the passage thereof through the means for detecting and interrupting an abnormal flow of dynamic or follow current to ground.

Lightning arresters, such as are used for the protection of distribution systems, transformers, and the like, occasionally fail and permit an abnormal ow of dynamic current through the arrester and the ground lead by which it is connected to ground. Such failures in arresters of the characteristic element type are usually due to the coring, fusing, or other impairment of the characteristic element by the passage of a lightning discharge, but failures may occur from other causes or in other types of arresters. Whatever cause of failure or type of arrester may be involved, it is desirable that the location of a failed arrester be indicated and that the flow of dynamic current to ground be interrupted since the short circuiting of the line to ground not only blows the protective fuses or circuit breakers, but also prevents the reactivation of the line and may result in a lockout.

My improved `disconnector or interrupter is designed to interrupt such ows to ground and comprises an electromagnet in series with a ground lead and activated by the ilow of dynamic current therethrough to control impact mechanism preferably of the explosive type, and conducting elements including electrodes forming an arc gap in series with the ground conductor and in parallel with the electromagnet and impact mechanism for diverting dynamic current through, and shunting lightning or surges of steep wave front around, the electromagnet and impact mechanism.

The electrical and impact constituents of my improved disconnector may be assembled in a small and compact shell of insulating material which may be seated in the base of conventional arresters without adding materially to the arrester length, or which may be interpolated between sections of the ground lead. The ability of a conventional type of arrester to discharge lightning is not appreciably diminished by the incorporation of my disconnector, which does not impair the direct path of lightning to ground. The inductance of the electromagnet diverts the lightning therefrom, and the operation of the lightning arrester normally interrupts the flow of dynamic or follow current before the explosive is detonated or any harm is done to the protected apparatus.

Should the lightning arrester fail to interrupt the ow of dynamic current within a predetermined time interval, ow of dynamic current through the electromagnet will result in the detonation of the explosive and the rupturing of the disconnector forcefully enough to expel the 2,957,967 vPatented Oct. 25, 1960 ground lead a distance suicient to interrupt the dynamic current ilow even when stiff ground wires are used.

The detonation of the explosive is preferably effected by providing a spring biased armature operable by the electromagnet and a cartridge having `a conductive shell the bias of the armature and of the number of ampere turns in the electromagnet coil.

The characteristic features and advantages of my improvements will further appear from the following description and the accompanying drawings in illustration thereof.

In the drawings, Fig. 1 is a vertical sectional view of a disconnector embodying my invention; Fig. 2 shows a disconnector embodying my invention incorporated in the base of a conventional type of lightning arrester shown in vertical section; Fig. 3 is an enlarged, transverse sectional view taken on the line 3 3 of Fig. 2; and Fig. 4 illustrates diagrammatically the incorporation of my disconnector in the ground lead of a conventional lightning arrester forming part of a distribution system.

The embodiment of my invention illustrated in the drawings comprises an insulating shell 1 having a hollow, cylindrical body connected by a weakened wall section 2 with an apertured bottom section 3, which has a conducting nut 4 threaded therein. A conducting cartridge holder 5 is seated on the bottom 3 in contact with the nut 4 and contains a socket 6 for the reception of a blank cartridge consisting of a conducting shell 7 filled with a suitable explosive and a detonator (not shown) in the upper portion thereof.

A conducting ring 8 encircles the base of the cartridge holder 5 and rests on the bottom 3 of the shell 1. The ring 8 supports an insulating spool 9, which has a hub containing a soft iron core 10. The external faces of, the flanges of the spool 9 are covered by paramagnetic shields 11 and 12.. The shield 12 has a down-turned flange 13 which encircles the periphery of an inductive coil 14 consisting of a suitable number of ampere turns of insulated wire. One end of the coil 14 passes through the bottom flange of the spool 9 and is electrically connected with the elect-rode 15 of a spring-biased armature 16 mounted on the spool ange and normally biasing the electrode 15 against the top of the shell 7.

The other end of the coil 14 passes through the upper flange of the spool 9 and through the shield 13 and is electrically connected with a cup shaped conductor 17 overlying the shield 13 and having a depending edge 18 encircling the ring 8 and forming therewith an arc gap 19 in shunt relation to the coil 14 and shell 7.

A conducting nut 20 is screwed into the threaded top flange 21 of the shell 1 until it presses firmly against the top of the member 17 and holds all the electrical and impact elements within the shell 1 in their assembled relation. The nut 2.0 may be provided with a threaded bore 22 for the attachment of a threaded conductor.

The nut 4 is provided with a threaded socket 23 for the lreception of a threaded bolt 24. A data plate 25 and complementary wire clamps 26 may be tightened 4against the shell 1 and against a ground conductor 2.7 by a nut 28.

As illustrated in Fig. 2, my improved disconnector may be readily incorporated in the base of a conventional lightning arrester A by inserting the shell 1 within the arrester flange B, with the nut 20 of the disconnector in close contact with the conducting bottom plate C of the arrester, and securing the disconnector in place by sealing compound 29.

The lightning arrester perse forms no partA of my invention, but in the form illustrated' comprises a wet porcelain body partially filled with a characteristic element, such as silicon carbide D, compacted. between the conducting bottom plate C and the conducting top plate E. An arc gap assembly F is inserted between thek retaining plate E and the conducting cover G, which is covered by a cap H and to which a line lead I may be connected.

Instead of mounting my improved disconnector di rectly in the base of the lightning arrester, it may have its nut 20 threaded on the end of a threaded conductor or a hanger .I of suitable length depending from the usual ground terminal of a lightning arrester, .as illustrated in Fig. 4.

In operation, lightning, or other dangerously high voltages on the line, arcs over the gaps of the assembly F and flows to ground through the silicon carbide D, and plate C of the arrester and through the members 20, 18, 8, 5 and 24 of the disconnector and through the lead 27 to ground. Such paths are in series and oifer low impedance to the passage of high voltages. As the voltage across the arrester decreases, impedance by the characteristic element automatically increases,v and if the arrester is in good condition all current flow ceases in a few microseconds.

If, however, there is any fault in the. arrester, dynamic current may follow surge current across the gaps of the arrester, but instead of owing across the gap 19 of the disconnector, the dynamic current will follow the path of lower impedance from the conductor 17, through the coil 14, electrode 15, shell 7, cartridge support 5, nut 4, bolt 24, and ground lead 27 to ground. As soon as the ilux generated by current ilow through the coil 14 is sufficient to overcome the spring biasing action of the 4armature 16, such armature is attracted by the core 10 and the electrode 15 is lifted up from the head of the cartridge 7. Current will, however, continue to` flow across the gap formed by the elevation of the electrode 15 from the head of the cartridge 7 and form an arc whose heat will detonate the detonator and explosive in the cartridge. This explosion will fracture the shell 1 around its area of weakness 2 and repel the base 3 and ground lead 27 connected therewith with considerable force before the line has been locked out. and to a distance ample to interrupt any current flow to ground.

It will be seen that my invention provides an inductive coil forming an electromagnet and offering high impedance to the passage of lightning therethrough and whose flux activates means for interrupting the flow of dynamic current therethrough, in combination with means providing a shunt path including electrodes forming an arc gap for diverting dynamic current through said inductive coil and shunting lightning around such coil to ground.

The displacement of the ground lead resulting from the ow of dynamic current through the electromagnetic coil not only interrupts the ground flow of dynamic current before a lockout occurs, but provides an indication of failure of the arrester readily visible from a remote distance.

Having vdescribed my invention, I claim:

1. In an electrical disconnector, the combination of an insulating housing having first and second electrodes; an electromagnet mechanism comprising an electromagnet electrically connected to said irst and second electrodes, an armature actuated upon the energization of the electromagnet by the dynamic current, said armature comprising the electrical path between said electromagnet and said second electrode, said mechanism including a portion relative to which said armature is movable upon actuation kby said electromagnet, due to the energization of the electromagnet, to form an arc lgap therewith; an explosive including a detonator in proximity with said arc and detonatable by the heat formed thereby, whereby said armature controls the electrical separation of said second electrode from said trst electrode, and means forming a shunt path for current surges above predetermined values around said electromagnet.

2. In apparatus of the character described, the combination of an insulating shell including a wall portion that is readily separable from the remainder of the shell, a container for an explosive supported by said wall portion, irst and second electrodes connected to said shell, an electromagnet electrically connected between said electrodes, an armature cooperating with said container, energization of said electromagnet by dynamic current retracting said electrode from said container for igniting the explosive, and two gap electrodes one `of which is electrically connected to the first electrode and the other to the second electrode for shunting surge current around said electromagnet, armature and container.

3. In apparatus of the character described, the combination of an insulating shell including a wall portion that is readily separable from the remainder of the shell, a conducting support seated on said wall portion, 4a container for an explosive seated on said conducting support, a first electrode connected to said shell, a second electrode encircling said support and container, said second electrode being connected to said wall portion, an electromagnet including a spool seated on said second electrode and an inductive coil wound on said spool, an armature controlled by said electromagnet; said inductive coil, said armature, and said container being in electrical series with each other; said coil being connected -electrically to the first electrode and said container being electrically connected to said second electrode, said armature being normally biased toward said container, energization `of said electromagnet by dynamic current retracting said electrode from said container to form an arc gap with said container for generating heat sucient to ignite the explosive, and two gap electrodes one of which is electrically connected to the first electrode and the other to the second electrode for shunting surge current around said electromagnet, armature and container.

References Cited in the file of this patent UNITED STATES PATENTS 1,009,748 Parsons Nov. 28, 1911 1,179,722 Heinritz Apr. 18, 1916 1,266,558 Creighton May 21, 1918 2,158,859 Horikoshi May 16, 1939 2,305,436 McMorris Dec. 15, 1942 2,551,858 Stoelting May 8, 2,860,210 Stoelting Nov. l1, 1958 

